1. Field of the Invention
The invention relates generally to ink cartridges, and more specifically, to ink cartridges comprising a pivotable member configured to pivot about a supporting shaft in an ink chamber.
2. Description of Related Art
A known image printing apparatus is configured to print an image on a sheet of paper with ink. The known image printing apparatus has an inkjet type print head, and selectively ejects ink droplets from nozzles of the print head toward the sheet of paper to print an image on the sheet of paper. A known ink cartridge is configured to be removably mounted to the known image printing apparatus, and the ink cartridge is configured to store ink therein and to supply the ink to the print head. When the known ink cartridge becomes empty of ink, the ink cartridge is removed from the image printing apparatus, and a new ink cartridge is mounted to the image printing apparatus. In order to determine the timing of replacement of the ink cartridge, a known detector is configured to detect the remaining amount of ink in the ink cartridge.
In a known ink cartridge, such as the ink cartridge described in JP-A-2005-262564, a float is configured to move in an ink chamber. The float is positioned at one end of a connecting member, and a light-blocking panel is positioned at the other end of the connecting member. A shaft is integrally positioned at the connecting member between the float and the light-blocking panel. The shaft is supported by a supporting base positioned at the bottom of the ink chamber, such that the connecting member is pivotable about the shaft in the ink chamber. The float is configured to move with buoyancy in accordance with the amount of ink in the ink chamber. The connecting member is configured to pivot according to the movement of the float, and the position of the light-blocking panel changes when the connecting member pivots. By optically detecting the change of the position of the light-blocking panel, the amount of ink in the ink chamber is determined.
In a known ink cartridge, the connecting member is manufactured by molding synthetic resin, the weight of which can be reduced to reduce frictional resistance when a connecting member pivots. Moreover, the shaft of the connecting member has a smaller diameter in order to reduce the frictional resistance with respect to the supporting base. Nevertheless, when the connecting member and the shaft are integrally formed of the synthetic resin, the smaller the diameter of the shaft is, the more difficult it becomes to center the center axis of the shaft. Because the molded product made of synthetic resin is subjected to burrs or steps generated by a parting line, it is difficult to smooth the peripheral surface of the shaft.
When the shaft is not integrally manufactured with the connecting member, the number of components increases in a supporting mechanism of the connecting member, and the shaft cannot be supported accurately at a predetermined position due to factors, such as imperfections due to a cumulative effect of the dimensional tolerances of the respective components, or positional displacements of supporting portions. Thus, the pivotal movement of the connecting member is hindered. Moreover, if the rattling of the connecting member with respect to the supporting mechanism is increased, the connecting member is easily tilted when the rattling increases, which may prevent the connecting member from pivoting smoothly. For example, the pivotal movement of the connecting member may be hindered when the connecting member contacts other members of the ink cartridge such as the inner wall of the ink chamber, or the connecting member may be stuck to the inner wall due to the surface tension of ink.